Fungal Genetics Reports
Volume 50
Article 8
Different cell types in Neurospora crassa
George N. Bistis
Drew University
David D. Perkins
Stanford University
Nick D. Read
University of Edinburgh
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Recommended Citation
Bistis, G. N., D.D. Perkins, and N.D. Read (2003) "Different cell types in Neurospora crassa," Fungal Genetics Reports: Vol. 50, Article 8.
https://dx.doi.org/10.4148/1941-4765.1154
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Different cell types in Neurospora crassa
Abstract
Neurospora possesses more cell types than are commonly recognized. We have been able to identify 28
morphologically distinct types. Having the cell types clearly defined will be important for genome annotation,
describing new mutant phenotypes, and determining sites of gene expression.
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This regular paper is available in Fungal Genetics Reports: http://newprairiepress.org/fgr/vol50/iss1/8
Number 50, 2003
17
Different cell types in Neu rospora crassa
George N. B istis1, David D. Perkins 2, and Nick D. Read3
1
Departm ent of B iology, Drew University, M adiso n, NJ 079 40, 2Departm ent of B iological Sciences, Stanfo rd U niversity,
Stanford, CA 94305-5020, 3Department of Cell and M olecular Biology, University of Edinburgh, Rutherford Building,
Edinburgh EH8 9QU, U.K.
Fungal Genet. Newsl. 50:17-19
Neurospora possesses more cell types than are commonly recognized. We have been able to identify 28
morphologically distinct types. Having the cell types clearly defined will be important for genome annotation, describing new
mutan t phenotypes, and d etermining sites of gene expression.
____________________________________________________________________________________
Neuro spora is a mo rphologically complex multicellular organism with ma ny more ce ll types than the unicellular yeast
Saccharomyces. Most workers are familiar with mycelia, macroconidia, perithecia, asci, and ascospores, but the diversity of
cell types produced by Neurospora may not be fully appreciated. Now that the products of specific genes can be localized
using G FP and o ther fluorescent proteins, attentio n will be fo cused increasingly on particular cell types that differ in
morpho logy, ph ysiology, or develop mental origin. D istinguishing different cell types is also imp ortant for genome annotation.
For convenience, we need to use the terms ‘cell’ and ‘cell type’ rather loosely to cover both cellular elements such as
hyphae and discrete cells such as spores (see discussion by Read, 1994 ). The basic undifferentiated, totipotent cellular element
is the compartmentalized vegetative hypha at the colony periphery (the leader hypha). Certain other cell types are comprised
of differentiated hyphae (e.g., fusion hyphae, ascogonia, trichogynes, ascogenous hyphae, asci, paraphyses, and periphyses). At
the other extreme are highly differentiated nonhyphal cells such as ascospores, microconidia, and the different wall cells of
protoperithecia and perithecia.
Twenty-eight morphologically distinct cell types are listed and described below. D esignation of protoperithecia and
microconidia as vegetative or sexual is arbitrary. Additional types or subtypes will no doubt be revealed.
Veg etative p hase
Lea der (lea ding ) hypha. This is a wide, fast-growing hypha located at the colony periphery. It consists of an apical, tipgrowing hyphal compartment interconnected with subapical compartments separated by perforated septa that provide
continuity by allowing the passage of nuclei, other organelles, and cytoplasm. The leader hyphae undergo subapical branching
and their gro wth contributes to the increase in colony diam eter (R obe rtson 1 965 ).
Trun k hyp ha. This is located in the colony interior. It is wide and composed of hyphal compartments that typically become
highly vacuolate. These hyphal compartments are typically shorter than those of leader hyphae because of the greater
frequency of septa. The septal pores of trunk hyphae are frequently occluded.
Fusion hypha. This is typically a narrow, dichotomously branching hypha that arises from a trunk hypha. It exhibits positive
tropisms, homing to ward s other fusion or trunk hyphae and anasto mosing with them (H ickey et al., 2002).
Aerial hyphae. In contrast to the hyphae described above which grow in or on the surface of solid or liquid media, aerial
hypha e grow away from the medium surface into the air. This is b elieved to be a result of forming hydro pho bic hyd rophob in
proteins on their surfac es (Sietsma and W essels, 1994 ).
Ma croconidiophore. The specialized hypha that gives rise to macroconidia (Springer and Y anofsky, 1989).
Macroconidium (blastoconidium). Large, multinucleate (typically 3-6 nuclei) asexual spore that grows and develops by
repeated budding of the apical cell of the conidiopho re (Springer and Y anofsky, 198 9). Impo rtant as a dispersal agen t and as a
male fertilizing agent.
Macroconidium (arthroconidium). Large asexual, multinucleate (typically 3-6 nuclei) spore that arises by fragmentation of the
conidiop hore (Springer and Y anofsky, 1989). Impo rtant as a dispersal agent and as a ma le fertilizing agent.
Macroconidial germ tube. Specialized hypha that emerges from the macroconidium and subsequently undergoes branching
and differentiates into the vegeta tive hyphae o f the young colo ny.
Macroconidial (conidial) anastomosis tube. Specialized hypha that emerges from the macroconidium but which is narrower
than the germ tube. It grows o nly a short distance and exhibits positive tropism s to othe r conidial ana stomo sis tubes with
which it fuses (M.G. Roc a and Read, unpub l.).
Microconidiophore. The specialized hypha that gives rise to microconidia (Maheshwari, 1999).
Microconidium. Small, uninucleate spo re that primarily functions as a male fertilizing agent (M aheshwari, 1999 ).
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Microconidial germ tube. Specialized hypha that emerges from a micro conidium but exhibits on ly limited growth
(Maheshwari, 1999 ).
Ascospore g erm tube. Spe cialized hypha that emerges from an asco spore (usually one at each end) and su bseq uently
unde rgoes branching and differentiates into the vegetative hyphae o f the young colo ny.
Sexua l phase
Ascogonium. A wide, coiled septate hypha that arises as a specialized branch of a trunk hypha (Read, 1983). It acts as the
‘female organ’ during fertilization.
Enveloping (or ascogonial investing) hyphae. Slender and highly branched hyphae that arise from the ascogonium or
surrounding vegetative hyphae, and which envelope and interweave around the ascogonium (Read, 1983). The fused
enveloping hyphae develop into the different cells of the protoperithecial wall (Read, 1994).
Trichogyne. Specialized narrow and often branched hypha that emerges from hyphal compartments of the ascogonium. It
exhibits a positive tropism toward ce lls of opposite mating type, with which it fuses and obtains fertilizing nuclei (Bistis,
1981).
Ascogenous hyphae. Specialized hyphae that arise from the ascogo nium and contain nuclei of bo th mating types. The se
hyphae generate asci from specialized cells within their croziers (Read and Beckett, 1995; Raju, 1980, 19 92).
Term inal (apical) crozier cell. Specialized apical compartment of the hook-shaped crozier. This cell, which is haploid and
uninucleate, gro ws aro und to ward the basal crozier cell with which it fuses to rec over the dikaryotic state (Read and B eckett,
199 6; Ra ju, 19 80, 1 992 ).
Basal (stalk) crozier cell. Spe cialized third co mpa rtment of a cro zier. T his cell, which is hap loid and uninucleate, fuses with
the terminal crozier cell to recover the dikaryotic state (Beckett and Read, 1996; Raju, 198 0, 19 92).
Pen ultimate cro zier cell (ascus m other cell). Second com partment of a crozier. This cell is initially dikaryotic and haploid. It
then becomes diploid after karyogamy has occurred, and develops into the ascus (Read and B eckett, 1996; Raju, 1980, 19 92).
Ascus. The specialized unbranched no nseptate hypha within which eight asco spores de velop . Its nucleus is initially diploid
but subsequently undergoes meiosis and an extra mitotic division to produce eight haploid nuclei. Each nucleus becomes
enclosed within an ascospore wall (Read and B eckett, 1996; Raju, 198 0, 19 92).
Ascospore. A thick-walled, pigmented spore with characteristic longitudinal ribs on its surface. Formed in the ascus following
meiosis. Initially uninucleate but later multinucleate. Haploid, with nuclei derived from one of the products of meiosis (Raju,
198 0, 19 92).
Paraphyses. Specialized multinucleate and branched hyphae possessing thin walls and interspersed between asci within the
perithe cium. T hey arise from centrum pseudop arenc hyma cells and from in between asci (Read and Beckett, 1985 ).
Centrum p seudo paren chym al cells. Pseudoparenchyma l cells derived from the fusion of the innermost layer of enveloping
hyphae. These thin-walled cells are initially very swollen in the protoperithecium but subsequently become flattened and form
the innermost layer of the two layered perithecial wall (Read and Beckett, 1986; Read , 1994).
Outer protoperithecial and perithecial wall cells (not neck). Thick-walled, pseudoparenchymatous cells with that are derived
from the fusion of the outer layer of enveloping hyphae (Read and Bec kett, 1985; Read, 1994).
Fringe hyph ae (hair cells). Slender, sometimes branched, hyphae that extend outward from protoperithecial and perithecial
wall cells (Read, 1983 ). Typically shorter than trichog ynes
Periph yses. Specialized short, slender and branched hyp hae which line the neck cana l. They possess multiple, multinucleate
hyphal compartments, and their tips bend towards the centre of the neck canal. They differentiate into the
pseudoparenchymatous neck wall cells around of rim of the ostiolar pore (Read and Becke tt, 1985).
Wall cell of perithecial neck. Pseudop arenc hymatous ce lls which, b eing derived from p eriphyses, are distinct from wall cells
of the lower bulbous region of the perithecium (Read and Beckett, 1985).
References
Bistis, G. N. 198 1. Chemotropic interactions between trichogyenes and conidia of opposite mating-type in Neurospora crassa.
Mycologia 73: 959-975.
Hickey, P. C., D. J. Jacobson, N. D. Read, and N . L. Glass 2002. Live-cell imaging of vegetative hyphal fusion in Neurospora
crassa. Funga l Genet .Bio l. 37: 109-119.
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DOI: 10.4148/1941-4765.1154
Number 50, 2003
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Maheshwari, R. 199 9. M icroconidia of Neurospora crassa. Funga l Genet. Bio l. 26: 1-18.
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Sietsma, J. H., and J. G. H. W essels 1994. Apical wall biogenesis. In The Mycota Vol 1, Growth, Differentiation and
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Springer, M. L., and C. Yanofsky 1989. A mo rphological and genetic analysis of conidiophore develop ment in Neurospora
crassa. Genes Devel. 3: 559-571.
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